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Crime Analysis for Problem Solvers in 60 Small Steps

Crime Analysis for Problem Solvers in 60 Small Steps
Step 52: Expect premature falls in crime

Offenders often believe that prevention measures have been brought into force before they actually have been started. This leads to what has been called the "anticipatory benefits" of prevention. Though these anticipatory effects can occur by accident, the police can make deliberate efforts to create or intensify them. To do so successfully, police must have useful insight into how offenders perceive the situation and have methods for deceiving offenders as to the true nature of the intervention.

Martha Smith and her colleagues found evidence of anticipatory benefits in 40% of situational prevention studies whose data could have revealed such benefits. They have suggested six possible explanations for observed anticipatory benefits:

  1. Preparation-anticipation effects occur when offenders believe the program is operational before it is actually working. For example, a property-marking program may be announced to the public, but residents have not yet been mobilized, or closed circuit television cameras may be installed but not yet monitored.
  2. Publicity/disinformation effects occur when offenders believe covert enforcement exists as the result of publicity or rumor. Offenders' perception can be manipulated, at least in the short run, through disinformation. Rather than disinformation, targeted communications can sometimes be effective. A Boston project to reduce youth homicide used direct communications with potential offenders to warn them that certain specified behaviors would result in crackdowns.
  3. Preparation-disruption effects occur when preparation for the prevention program causes surveillance at the prevention sites. Surveys of residents might alert offenders. Problem-solving projects can create anticipatory responses during their analysis stage if there is considerable visible enquiry in the community. In the late 1980s as part of the analysis of a burglary problem, members of the Newport News Police Department conducted door-todoor surveys in a high burglary neighborhood. This may have contributed to the subsequent fall in burglaries. In their review of effective policing strategies, Sherman and Eck noted that door-to-door police contacts have generally been found to have a crime reduction effect.
  4. Creeping implementation occurs when parts of the response are put into effect before the official start date. The evaluator may use June 1st as the beginning of the full program, but offenders detect staged implementation in the weeks leading up to June 1, and change their behavior accordingly.
  5. Preparation-training effects occur when planning, training, and surveys make the public or police better prepared to address problems and they use this new knowledge prior to the program going into effect. A coordinated multi-business anti-shoplifting program, for example, may be scheduled to begin on a particular date, but the discussions and training of employees makes them more attentive prior to that date.
  6. Motivation of officers or public occurs for similar reasons as preparation training, except the people involved are more highly motivated rather than better equipped. The higher motivation leads to improved performance in advance of response implementation.

Using a timeline to carefully document when pieces of the response were implemented is helpful for showing that an anticipatory effect is plausible (see Step 46).

Smith and her colleagues also identified four distinct circumstances that masquerade as anticipatory effects, but are really the results of misinterpretation or incomplete analysis:

  1. Seasonal changes can create pseudo anticipatory effects when an intervention begins shortly after a seasonal turndown in crime. Controlling for seasonality (Steps 26 and 47) can eliminate this problem.
  2. Regression effects refer to natural declines in crime from extreme highs that occur even if nothing is done (Step 47). If a crime trend for a problem has just dropped due to a regression effect and a prevention program is implemented, the natural decline will look like an anticipatory effect. Examining the long-term average crime level (Step 26) prior to the response, as suggested in Step 47, can reveal a regression effect masquerading as an anticipatory effect.
  3. If a crime type (A) has been over-recorded by changing the classification of another crime, it is possible to get what looks like an anticipatory effect. This might occur if one type of crime was inflated in order to gain funding to address that type of crime, and then following the receipt of funding, the classification was changed back to normal. This bogus anticipatory effect can be detected by looking at opposite trends in the other crime. Finding two similar crimes that have opposite trends provides a clue that classification changes may be responsible.
  4. Smoothing data (Step 26) to reveal a trend masked by random variation can produce results that look like anticipatory effects. The wider the moving average (5 periods rather than 3, for example) and the bigger and more abrupt the decline in crime following the intervention, the more likely smoothing could create a pseudo anticipatory effect. Comparing smoothed and unsmoothed data will reveal this pseudo anticipatory effect.

Anticipatory Effects of Publicity

Paul Barclay and colleagues evaluated the effects of bike patrols on auto theft from a large commuter parking lot outside Vancouver, British Columbia. Vehicle theft dropped after the response, but it had been dropping for several weeks prior to the bike patrols, since the implementation of a publicity campaign that preceded the bike patrols. In this case, an anticipatory effect may have added a great deal to the overall effectiveness of the patrols. Though a moving average was used to smooth out random variation, the drop in thefts between the beginning of the publicity and the beginning of the bike patrols is too large to be due to data smoothing.

Anticipatory Effects of Publicity

Source: Barclay, Paul and colleagues (1996) "Preventing Auto Theft in Suburban Vancouver Commuter Lots: Effects of a Bike Patrol." Crime Prevention Studies, volume 6, Monsey, NY: Criminal Justice Press.

Read More

  • Sherman, Lawrence and John Eck. 2002. Policing for Crime Prevention. Pp. 295-329 in Evidence-Based Crime Prevention, edited by Lawrence Sherman and colleagues. New York: Routledge.
  • Smith, Martha and colleagues (2002). Anticipatory Benefits in Crime Prevention. In Analysis for Crime Prevention. Crime Prevention Studies, Volume 13. Monsey, New York: Criminal Justice Press.